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(From CP47, Page 11, January, 1986)

     We have used NYLON NYLAFLOW brake lines in all of the RAF designs so far with very low required maintenance. There are a few points that require care and if you do sloppy work here, you may set yourself up for a potential brake failure. If this occures after a period of hard braking, it is even possible to have a brake fire. This could have serious consequences, so do not take this lightly.
     First of all, NYLON lines must never be stored where they get exposed to direct sunlight. An excellent idea would be to store your roll of brake line in a black plastic bag until you are ready to install it. After it is installed, paint it with black or silver paint. Do not roll it out into the sunlight without wheel pants or paint to protect it.
     Heat can soften the Nylaflow and allow it to expand under pressure, and possibly even burst if the heat is excessive. For this reason, it is very important to route the brake lines as far as possible from the brake disc. Keep in mind that under heavy breaking the disc can get very, very hot. This heat radiates toward the gear leg, (which must be insulated with several layers of fiberfrax siliconed to the strut) and if the brake line passes between the strut and the disc, you have set yourself up for a potential disaster. The brake line must pass inboard of the strut, which keeps the strut between the disc and the brake line. In addition we strongly recommend insulating the brake line with fiberfrax. We cut a long narrow strip, perhaps 5/8" wide, applied silicone to the fiberfrax and wound it around and around the brake line until it was covered from where it appeared out of the trailing edge of the strut to the nut on the fitting on the caliper. A little tape will hold it in place, slip a piece of heat shrink tubing over the whole thing and shrink it down onto the fiberfrax. We also wrap this in aluminum foil, which of course helps by reflecting any radiated heat.
     If you have not taken any of the above measures and have been operating your airplane for any length of time, the chances are that you way already have caused heat damage to the nylon line. Repeated heat applications to a sample piece of Nylaflow have shown that it causes embrittlement. It becomes stiff and when you try to bend it, it may break. If you have this problem you should replace the brake lines. This is not as hard as it may sound. We have done it a few times ourselves. Use a dremel with a small saw, 3/8" - 112" diameter, cut throught the glass into the brake line at the trailing edge, full length from fuselage to wheel. Grab one end of the brake line and pull it out through the saw cut. Install a new piece by opening the saw cut and carefully working it in full length of each gear leg. Layup a thin ply of hobby store glass or one ply of BID to retain it in the trailing edge of the gear and you have it. The whole operation can be done in an hour!
wpe1E.gif (5053 bytes)      We have recentIy instaIIed "NyloseaI " nyIon tubing in two of our aircraft for brake lines and, so far, it looks very good. We only have a few hundred hours of test time at this point, but we are pleased with its performance. All of the above precautions were, of course observed. One of the best ideas to avoid heat problems associated with heavy breaking, is to cut vent holes in the highest point in the wheel pants (aircraft parked nose down). This allows trapped hot air to rise out of the wheel pant, drawing in cold air to cool the hot disc.
     For new construction, a good suggestion would be to install a hardware store type plastic tube into the trailing edge, such that the brake lines way be slipped through for easy removal if it should ever become necessary. You would need to find a plastic tube with about a 3/16" to 1/4" I.D.  The stiff type of hardware store plastic tube would be best.